1. Field of the Invention
The present invention relates to an exhaust gas purifying apparatus, and more particularly, it relates to an exhaust gas purifying apparatus using a metallic carrier suited to being coated with a catalyst.
2. Description of Related Art
There are various known exhaust gas purifying apparatuses for purifying exhaust gases from an internal combustion engine. For instance, a known exhaust gas purifying apparatus includes a metal carrier which carries a catalyst to accelerate chemical reactions with pollutants (HC, CO, NOx, etc.) contained in the exhaust gases, such as an oxidization or a deoxidization to thereby reduce or eliminate the pollutants during the passage of the exhaust gases therethrough. In general, a conventional metal carrier suited to being coated with a catalyst is comprised of a thin flat metal plate and a corrugated thin metal plate, which are superimposed and rolled into a honeycomb shape. The honeycomb shaped metal carrier thus produced is received and secured in a cylindrical metal casing to form a catalytic converter. Also, a carrier suited to being coated with a catalyst having a turbulence producing portion which causes a haphazard secondary motion within the exhaust gases has been recently proposed to enhance the activity of the catalyst. The turbulence caused by the turbulence producing portion within the high temperature exhaust gases contributes to an enhancement of a temperature increasing effect at the turbulence producing portion, so that the activation of the catalyst at the turbulence producing portion of the carrier can be accelerated. Consequently, the purification of the exhaust gases begins at an early stage of the starting of the engine, and accordingly, the reaction heat produced by the purification can be also effectively utilized. Thus, the catalytic converter can be activated as a whole within an extremely short space of time, in comparison with the conventional exhaust gas purifying apparatuses.
However, in the known carrier having the turbulence producing portion, as mentioned above, since the temperature of the turbulence producing portion is very high even after the activation of the catalyst, the aging of the catalyst carried by the turbulence producing portion is promoted, thus resulting in an early reduction in the exhaust gas purifying efficiency.